“Feel free. We will have it tanned and stuffed and sell it for a fortune. A dwarf’s cock has magical powers.”
A Dance With Dragons
I don't think everybody believed that dwarf’s cock has magical powers. Especially in Westeros were parents don't like dwarf kids because if everybody believed that dwarf’s cock has magical powers they would have hunted down all the dwarfs.
I haven't seen the episode yet but in the books Tyrion was sold as dwarf who could amuse people.
Lot ninety-seven.” The auctioneer snapped his whip. “A pair of dwarfs, well trained for your amusement.”
The auction block had been thrown up where the broad brown Skahazadhan flowed into Slaver’s Bay. Tyrion Lannister could smell the salt in the air, mingled with the stink from the latrine ditches behind the slave pens. He did not mind the heat so much as he did the damp. The very air seemed to weigh him down, like a warm wet blanket across his head and shoulders.
“Dog and pig included in lot,” the auctioneer announced. “The dwarfs ride them. Delight the guests at your next feast or use them for a folly.”
A Dance With Dragons
Because it feels like people weren't really interested in buying a dwarf. I say this because Tryion was sold as clown rather than a person possessing a cock of magical powers.